American Board of Internal Medicine (ABIM) Certification Practice Exam

What is true regarding the contagion period of smallpox?

1. Patients are infectious immediately after exposure

2. Patients remain contagious until all scabs and crusts are shed

3. Patients are only contagious during the rash phase

4. Patients are not contagious until symptoms develop

The correct answer is: Patients remain contagious until all scabs and crusts are shed

The correct understanding of the contagion period of smallpox states that patients remain contagious until all scabs and crusts are shed. In smallpox, transmission typically occurs during the later stages of the illness. Specifically, individuals infected with smallpox can spread the virus from the time symptoms appear until the last scab falls off, which usually occurs several weeks later. This means that the possibility of spreading the virus exists not only during the initial rash phase but throughout the progression of the disease until complete recovery. While patients begin to show symptoms before the scabs form, their potential to infect others is highest as the sores develop and until they fully heal. Therefore, understanding this timeline is critical for effective isolation practices and preventing transmission in healthcare and community settings. This knowledge underscores the importance of monitoring patients until they are fully cleared of scabs, ensuring they are no longer a risk to others.